Liner for in-ground lng storage facility



Sept. 22, 1970 c; T JRH' ET AL 3,529,426

LINER FOR IN-GROUND LNG STORAGE FACILITY Filed Aug. 2, 1968 I INVENTORS. I Russell C. Proctor Jr. Henry Wemsfem wwaw United States Patent ice US. Cl. 61.5 7 Claims ABSTRACT OF THE DISCLOSURE An underground storage facility for liquefied natural gas utilizing a storage hole having sides defined by a rock wall has a liner which prevents the storage liquid from contacting the sidewall and bottom of the hole so that fissures in such wall cannot act as individual heat pumps which would be the case if the liquid could flow into such fissures. A base is constructed at the bottom of the hole and has an upper surface presented by a layer of concrete. An open top, cylindrical, upright liner is suspended within the hole with its bottom in contact with the con-- crete layer to form a receptacle for the LNG. The sidewall of the liner is suspended from structure at the top of the hole so that a thin wall metal plate construction may be used :without the necessity for such plate to be sufficiently thick for the sidewall to be self-sustaining. In addition, the sidewall supports are adjustable to compensate for expansion and contraction of the sidewall under temperature variations. .A space between the liner and the earth wall permits a part of the boil-off gas to pass in thermal contact with the earth wall to maintain the latter at a cold temperature. A gathering header at the bottom of the space provides a means of removing condensed liquid therefrom.

Underground storage of liquefied natural gas is advantageous from the standpoint of safety. An aboveground storage facility, even if precautions are taken to prevent the flow of liquefied gas into surrounding areas in the event that a tank should rupture, inherently presents a hazard to some degree, particularly when located in close proximity to populous areas.

In an underground facility, a large hole is excavated after the surrounding earth is first frozen to prevent collapse of the earth wall formed by the excavation. A suitable base is laid in the bottom of the hole and, heretofore, the latter has been subsequently filled with the lique- =fied gas. Being in direct contact with the earth or rock wall of the storage receptacle, the moisture in the wall is maintained frozen because of the extremely cold temperature (--260 F.) of the liquefied gas. Thus, from the time excavation commences until the hole is actually filled with LNG, the wall is not permitted to thaw and is, therefore, permanently maintained at a very cold temperature to preserve its structural integrity.

It may be appreciated, however, that the introduction of LNG into the hole effects a considerably greater cooling of the wall structure defining the hole than is the case during excavation by refrigerant-containing freeze tubes placed in the ground for the purpose of preventing the collapse of the wall. Since the wall is normally primarily rock, fissures may be formed because of contraction and attendant cracking of the rock under the temperature of the LNG. These fissures, extending both vertically and horizontally, would thereby tend to provide a multiplicity of intercommunicating passages within the wall adjacent the hole. As to those which present essentially vertically disposed loops with portals spaced vertically on the wall surface, a heat pump effect would thus be produced since 3,529,426 Patented Sept. 22, 1970 the LNG flowing into the lower leg of each loop would be warmed and partially vaporized to an extent to lower its specific gravity whereby the mixture could then rise in a vertical leg and finally be expelled back into the hole through another horizontal passage. The ultimate result would be a significant increase in boil-off and thus require that the refrigeration plant of the facility have increased capacity as compared with a more eflicient storage receptacle with a lesser inherent boil-oif rate.

It is, therefore, the primary object of this invention to provide a means of preventing excess boil-off in underground liquefied gas storage facilities that may be subject to the rock cracking problem discussed above.

As a corrolary to the foregoing object, it is an important aim of the instant invention to provide a liner for underground earth storage receptacles to minimize contact of the liquefied gas with the earth wall and bottom thereof and yet maintain the same sufficiently cold to assure that the moisture therein remains frozen and the wall thereby remains structurally strong.

Another important object of the invention is to provide an underground storage facility for liquefied gas having a liner as aforesaid which is suspended within the hole, and wherein means is provided for supporting the sidewall of the liner while at the same time permitting compensation for expansion and contraction of the liner sidewall under variations in temperature.

In the drawing:

FIG. 1 is a vertical sectional view of an LNG storage hole showing the liner of the instant invention in place therein; and

FIG. 2 is an enlarged, fragmentary, vertical sectional view showing two of the hangers in detail utilized to suspend the liner.

A storage hole 10 suitably formed by excavation in a conventional manner is defined by an earth wall 12 and a base broadly denoted 14. The hole 10 is generally cylindrical in configuration and is covered by a closure 16 in the form of a concrete inner roof 18 and a metal outer roof or dome 20. A housing 21 for supply pumps is illustrated on top of the dome 20. The circumferential periphery of the inner roof 18 is supported by a cylindrical wall 22 resting on a footing 24 which is supported by a shoulder defined by the earth wall 12 and disposed just beneath ground level at the top of hole 10. If desired, the space between the inner and outer roofs 18 and 20 may be filled with insulation.

A dividing line 26 in the ground illustrates that typically, for example, the earth above line 26 is primarily soil, while the earth below line 26 is primarily rock. Thus, since hole 10 would normally extend to a substantial depth, the wall 12 is primarily rock throughout the surface area thereof which, in underground facilities heretofore, would be in direct contact with the liquefied gas in hole 10.

The base 14 comprises a sand pad 28 directly overlying the earth at the bottom of hole 10, a layer of glass foam blocks 30 being laid on top of pad 28. The blocks 30 have good insulating properties and are covered by a layer of concrete 32 which serves as a ballast to hold the blocks 30 in place.

The vertical pipes 34 seen in FIG. 1 adjacent the surface of wall 12 are the freeze pipes utilized during excavation to freeze an annular zone of earth defining the lateral boundary of the excavation. Thus, as mentioned above, the moisture within wall 12 adjacent its inner surface is frozen solid during excavation to provide the surrounding earth with sufficient structural strength to preclude collapse thereof.

An upright, cylindrical liner 36 is disposed in hole 10 and the sidewall thereof is supported by a plurality of extensible hangers 38 spaced circumferentially around closure 16. The liner 36 is open at its upper end and has a thin, metallic wall 40 joined to a metallic bottom 41. The wall 40 and bottom 41 are preferably composed of either a 9% nickel steel or stainless steel and is designed to resist the hydrostatic pressure of the LNG. A layer of urethane foam insulation 42 is secured to the outer surface of the liner wall 40 and extends the entire length of such wall.

The outside, transverse dimension of the liner wall 40 is less than the distance across hole '10, and the liner 36 is coaxially disposed within hole to define an annular open space 44 between the liner and the surface of the earth wall 12. A boil-off gathering header 46 in the form of a slotted ring is disposed in space 44 at the bottom thereof on base 14, the header 46 being in communication with the suction eside of a pump 48 through a conduit 50.

Referring particularly to FIG. 2, each of the hangers 38 includes an upright sleeve 52 secured to the inner roof 18 and a hanger member in the form of an upright rod 54. Each of the hanger rods 54 is attached to the upper end of the metal liner wall 40 by a clevis and pin connection 56. The upper end of each hanger rod 54 is threaded and extends through an opening in the clos d upper end of sleeve 52 to receive a nut 58 that overlies the end of the sleeve. The hangers 38 are normally covered by caps 60 which may be removed to permit adjustment of nuts 58 to raise and lower the liner 36. The construction of the liner 36 is particularly apparent in FIG. 2 where a weld seam 62 is shown at the joined edges of each adjacent pair of vertically extending, transversely arcuate plates 64. The use of nickel or stainless steel in the construction of liner 36 is preferred in order to provide a plate material capable of withstanding the extremely low temperature of the liquefied gas.

In use, the hangers 38 are initially adjusted so that the liner 36 is suspended within hole 10 in disposition with bottom 41 in contact with the upper surface of the concrete layer 32 of base 14. While the principal weight of sidewall 40 is carried by the hangers, as liquefied gas is introduced into the hole, the liner 36 slowly contracts and nuts 58 are adjusted to compensate for contraction of sidewall 40. Since the earth surrounding liner 36 always remains cold and only rarely is the liner 36 completely exhausted of liquefied gas, adjustment of the hangers to compensate for expansion of liner wall 36 is also required only at infrequent intervals.

In this respect, it should be understood that a certain amount of cold or liquefied gas in space 44 is desired, and for this purpose the thickness of the insulation 42 on the liner wall 40 is selected to permit sufiicient boil-off to maintain the moisture within the earth wall 12 in the frozen state. More particularly, as boil-off occurs, the boil-off gas passes over the lip or upper end of liner 36 and then downwardly through the annular space 44 whereupon, during such passage, the boil-off gas is brought into thermal contact with the surface of the earth wall 12. The boil-off in liquid form collecting at the bottom of space 44 is gathered by the header 46 and pumped from space 44 by the pump 48. The maximum level of the liquid within liner 36 is indicated by the broken line 68.

At this juncture, it is instructive to appreciate that the surface presented by an earth bank such as the wall 12 of soil and rock composition is not as naturally suitable for confining liquefied gas as caverns in salt formations utilized for storage purposes in some parts of the United States. A salt formation presents a smooth wall surface and has low thermal conductivity, while the earth wall '12 does not present a smooth surface and has greater thermal conductivity than the insulated liner 3 6. These characteristics, in conjunction with the fissure problem discussed hereinabove, render the utilization of liner 36 important if an efficient underground storage facility is to be provided. Cracking of the rock wall is illustrated in FIG. 1 by the various fissures 70 extending both horizontally and vertically adjacent the surface of wall 12 and at the bottom of hole 10.

If necessary as required by changing temperature conditions, the nuts 58 of the hangers 38 may be adjusted to compensate for expansion and contraction of the liner wall 40 to maintain the bottom 41 of the liner 36 in contact with the concrete layer 32. In the case of expansion, excess vertical compressional loading could be placed on the wall 40 of the liner, requiring that the hangers 38 be adjusted to raise the upper end of the liner wall 40 to reduce the compressional load on the vertical plates 64. It should be understood that the plates 64 are strong in tension and hence, being suspended, permit the use of minimum thickness plates which otherwise would fail in vertical compression or bending if supported only at the bottom. Contraction of the sidewall 40 would produce a destructive force on the line or joinder of bottom 41 to sidewall 40 in the absence of appropriate adjustment of hangers 38.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In the storage of a liquefied gas in a hole in the ground defined by an upright frozen earth wall and a base presenting the bottom of the hole, the improvement comprising:

a tubular, upright liner,

said liner defining a gas storage area and having an outside transverse dimension less than the distance across said hole,

hanger means suspending the liner in the hole with the lower extremity thereof engaging said base,

said hanger means positioning the liner in the hole to define an open space circumscribing the liner between the latter and said wall,

said liner having an upper end communicating said area with said open space whereby boil-off gas from said area is directed to flow downwardly through said open space to maintain said earth wall in a frozen state.

2. An improvement as claimed in claim 1,

and a gathering header in said open space communicating with the latter and disposed adjacent said base in at least partially surrounding relationship to said liner,

there being pump means communicating with said header for pumping the boil-off gas from the open space.

3. An improvement as claimed in claim 1,

said liner having insulating material secured thereto having a thickness to maintain the temperature of said gas in said area at a level to cause the rate of flow of said boil-off gas to be sufiicient to maintain said earth wall in a frozen state.

4. An improvement as claimed in claim 1,

said liner comprising a thin-walled, metallic cylinder having a sidewall of relatively high strength in tension and capable of withstanding said temperature variations,

said hanger means being connected with said liner exclusively at its upper end.

5. An improvement as claimed in claim 1,

and a bottom connected to said sidewall of the liner in contact with said base to preclude substantial leakage of liquified gas from the liner into said open space.

6. An improvement as claimed in claim 5,

said hanger means being extensible to compensate for expansion and contraction of the liner and thus assure that the bottom thereof is maintained in contact with said base as the temperature of the liner changes.

7. An improvement as claimed in claim 1,

said earth wall defining a shoulder within said hole;

a footing supported by said shoulder;

wall means extending upwardly from said footing; and

a closure over said hole supported by said wall and providing support for said hanger means.

(References on following page) 6 References Cited 3,167,209 1/1965 Jones 220-15 X EN 3,331,525 7/1967 Coehn 220-15 UNITED STATES PAT TS 3,379,012 4/1968 Jackson 61-.5 10/1936 Peyrouze 61.5 X 11/1943 Klingberg 61.5 5 FOREIGN PATENTS 323;;- f 3 1,158,536 12/1963 Germany. 4/1963 Dosker. 7/1963 Schroeder X PETER M.CAUN,Pr1mary Exammer 9/ 1964 Schlumberger. 

